First communication device and methods therein, for sending one or more control signals to a second communication device

ABSTRACT

A method performed by a first communication device ( 101 ) for sending one or more control signals to a second communication device ( 102 ). The first communication device ( 101 ) and the second communication device ( 102 ) operate in a wireless communications network ( 100 ). The first communication device ( 101 ) determines ( 901 ), during a first period, that a transmission medium is available for sending the one or more control signals to the second communication device ( 102 ). The first communication device ( 101 ) then sends ( 902 ), to the second communication device ( 102 ), the one or more control signals along with a discovery signal, via the transmission medium. The discovery signal and the one or more control signals are sent without data after the first period. The first period is shorter than a second period for determining that the transmission medium is available for sending the data.

TECHNICAL FIELD

Embodiments herein relate to a first communication device and methodstherein for sending one or more control signals to a secondcommunication device. Embodiments herein further relate to computerprograms and computer-readable storage mediums, having stored thereonthe computer programs to carry out these methods.

BACKGROUND

Communication devices such as terminals are also known as e.g. UserEquipments (UE), mobile terminals, wireless terminals, wireless devicesand/or mobile stations. Terminals are enabled to communicate wirelesslyin a cellular communications network or wireless communication system,sometimes also referred to as a cellular radio system or cellularnetworks. The communication may be performed e.g. between two terminals,between a terminal and a regular telephone and/or between a terminal anda server via a Radio Access Network (RAN) and possibly one or more corenetworks, comprised within the cellular communications network.

Terminals may further be referred to as mobile telephones, cellulartelephones, laptops, or surf plates with wireless capability, just tomention some further examples. The terminals in the present context maybe, for example, portable, pocket-storable, hand-held,computer-comprised, or vehicle-mounted mobile devices, enabled tocommunicate voice and/or data, via the RAN, with another entity, such asanother terminal or a server.

The cellular or wireless communications network covers a geographicalarea which may be divided into cell areas, wherein each cell area may beserved by an access node such as a base station, e.g. a Radio BaseStation (RBS), which sometimes may be referred to as e.g. evolved NodeB“eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station),depending on the technology and terminology used. The base stations maybe of different classes such as e.g. macro eNodeB, home eNodeB or picobase station, based on transmission power and thereby also cell size. Acell is the geographical area where radio coverage is provided by thebase station at a base station site. One base station, situated on thebase station site, may serve one or several cells. Further, each basestation may support one or several communication technologies. The basestations communicate over the air interface operating on radiofrequencies with the terminals within range of the base stations. In thecontext of this disclosure, the expression Downlink (DL) is used for thetransmission path from the base station to the mobile station. Theexpression Uplink (UL) is used for the transmission path in the oppositedirection i.e. from the mobile station to the base station.

In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE),base stations, which may be referred to as eNodeBs or even eNBs, may bedirectly connected to one or more core networks.

3GPP LTE radio access standard has been written in order to support highbitrates and low latency both for uplink and downlink traffic. All datatransmission is in LTE controlled by the radio base station.

The 3GPP initiative “License-Assisted Access” (LAA) intends to allow anLTE equipment, such as a communication device, to also operate in theunlicensed 5 GigaHertz (GHz) radio spectrum. The unlicensed 5 GHzspectrum may be used as a complement to the licensed spectrum.Accordingly, communication devices may connect in the licensed spectrum,through e.g., a primary cell or PCell, and may use Carrier Aggregation(CA) to benefit from additional transmission capacity in the unlicensedspectrum, through e.g., a secondary cell or SCell. To reduce the changesrequired for aggregating licensed and unlicensed spectrum, the LTE frametiming in the PCell may be simultaneously used in the SCell.

Regulatory requirements, however, may not permit transmissions in theunlicensed spectrum without prior channel sensing. Since the unlicensedspectrum may be shared with other radios of similar or dissimilarwireless technologies, a so called Listen-Before-Talk (LBT) method mayneed to be applied. The LBT procedure may involve sensing a medium for apre-defined minimum amount of time, and backing off if the channel isbusy. Today, the unlicensed 5 GHz spectrum is mainly used by equipmentimplementing the Institute of Electrical and Electronics Engineers(IEEE) 802.11 Wireless Local Area Network (WLAN) standard. This standardis known under its marketing brand “Wi-Fi.”

LTE

LTE may use Orthogonal Frequency Division Multiplexing (OFDM) in the DLand Discrete Fourier Transform (DFT)-spread OFDM, also referred to asSingle-Carrier Frequency Division Multiple-Access (SC-FDMA), in the UL.The basic LTE DL physical resource may thus be seen as a time-frequencygrid as illustrated in FIG. 1, where each resource element correspondsto one OFDM subcarrier during one OFDM symbol interval. The UL subframemay have the same subcarrier spacing as the DL, and the same number ofSC-FDMA symbols in the time domain as OFDM symbols in the DL. Thesubcarrier spacing has been chosen to be 15 kiloHertz (kHz), as shown.Each resource element may comprise a so-called cyclic prefix, which isinvolved in preventing inter-symbol interference.

In the time domain, LTE DL transmissions are organized into radio framesof 10 milliseconds (ms), each radio frame consisting of tenequally-sized subframes of length Tsubframe=1 ms as shown in FIG. 2,which illustrates the LTE time-domain structure. Each subframe comprisestwo slots of duration 0.5 ms each, and the slot numbering within a framemay range from 0 to 19. For normal cyclic prefix, one subframe mayconsist of 14 OFDM symbols. The duration of each symbol is approximately71.4 microseconds (μs).

Furthermore, the resource allocation in LTE may typically be describedin terms of resource blocks, where a resource block corresponds to oneslot, 0.5 ms, in the time domain and 12 contiguous subcarriers in thefrequency domain. A pair of two adjacent resource blocks in the timedirection, 1.0 ms, may be known as a resource block pair. Resourceblocks may be numbered in the frequency domain, starting with 0 from oneend of the system bandwidth.

Downlink transmissions may be dynamically scheduled, i.e., in eachsubframe the base station may transmit control information about whichterminals data is transmitted to, and upon which resource blocks thedata is transmitted, in the current DL subframe. This control signalingmay be typically transmitted in the first 1, 2, 3 or 4 OFDM symbols ineach subframe, and the number n=1, 2, 3 or 4 is known as the ControlFormat Indicator (CFI). The DL subframe may also contain commonreference symbols, which may be known to the receiver, and used forcoherent demodulation of e.g., the control information. A DL system withCFI=3 OFDM symbols as control region is illustrated in FIG. 3, whichillustrates a normal DL subframe. The control region in FIG. 3 is shownas comprising control signaling, indicated by black squares, referencesymbols, indicated by striped squares, and unused symbols, indicated bycheckered squares.

From 3GPP LTE Release 11 onwards, the above described resourceassignments may also be scheduled on the enhanced Physical DownlinkControl Channel (EPDCCH). For Release 8 to Release 10, only PhysicalDownlink Control Channel (PDCCH) is available.

The reference symbols shown in the above FIG. 3 are the Cell-specificReference Symbols (CRS) and they may be used to support multiplefunctions including fine time and frequency synchronization and channelestimation for certain transmission modes.

Physical Downlink Control Channel (PDCCH) and Enhanced PDCCH (EPDCCH)

The PDCCH and/or EPDCCH may be used to carry DL Control Information(DCI) such as scheduling decisions and power-control commands. Morespecifically, the DCI may include:

a) Downlink scheduling assignments, including the Physical DL SharedCHannel (PDSCH) resource indication, transport format, hybrid-AutomaticRepeat reQuest (ARQ) information, and control information related tospatial multiplexing, if applicable. A DL scheduling assignment may alsoinclude a command for power control of the Physical Uplink ControlCHannel (PUCCH) used for transmission of hybrid-ARQ acknowledgements inresponse to DL scheduling assignments.

b) Uplink scheduling grants, including Physical UL Shared CHannel(PUSCH) resource indication, transport format, and hybrid-ARQ-relatedinformation. An UL scheduling grant may also include a command for powercontrol of the PUSCH.

c) Power-control commands for a set of terminals as a complement to thecommands included in the scheduling assignments/grants.

One PDCCH and/or EPDCCH may carry one DCI message containing one of thegroups of information listed above. As multiple terminals may bescheduled simultaneously, and each terminal may be scheduled on both DLand UL simultaneously, there may be a possibility to transmit multiplescheduling messages within each subframe. Each scheduling message may betransmitted on separate PDCCH and/or EPDCCH resources, and consequently,there may be typically multiple simultaneous PDCCH and/or EPDCCHtransmissions within each subframe in each cell. Furthermore, to supportdifferent radio-channel conditions, link adaptation may be used, wherethe code rate of the PDCCH and/or EPDCCH may be selected by adapting theresource usage for the PDCCH and/or EPDCCH, to match the radio-channelconditions.

Here follows a discussion on the start symbol for PDSCH and EPDCCHwithin the subframe. The OFDM symbols in the first slot may be numberedfrom 0 to 6. For transmissions modes 1-9, the starting OFDM symbol inthe first slot of the subframe for EPDCCH may be configured by higherlayer signaling and the same may be used for the corresponding scheduledPDSCH. Both sets may have the same EPDCCH starting symbol for thesetransmission modes. If not configured by higher layers, the start symbolfor both PDSCH and EPDCCH may be given by the CFI value signaled in thePhysical Control Format Indicator CHannel (PCFICH).

Multiple OFDM starting symbol candidates may be achieved by configuringa UE in transmission mode 10, by having multiple EPDCCH PhysicalResource Block (PRB) configuration sets where for each set the startingOFDM symbol in the first slot in a subframe for EPDCCH may be configuredby higher layers to be a value from {1,2,3,4}, independently for eachEPDCCH set. If a set is not higher layer configured to have a fixedstart symbol, then the EPDCCH start symbol for this set may follow theCFI value received in the PCFICH.

Carrier Aggregation

The LTE Release 10 standard may support bandwidths larger than 20MegaHertz (MHz). One requirement on LTE Release 10 may be to assurebackward compatibility with LTE Release 8. This may also includespectrum compatibility. That may imply that an LTE Release 10 carrier,wider than 20 MHz, may appear as a number of LTE carriers to an LTERelease 8 terminal. Each such carrier may be referred to as a ComponentCarrier (CC). In particular, for early LTE Release 10 deployments, itmay be expected that there may be a smaller number of LTE Release10-capable terminals compared to many LTE legacy terminals. Therefore,it may be necessary to assure an efficient use of a wide carrier alsofor legacy terminals, i.e., that it may be possible to implementcarriers where legacy terminals may be scheduled in all parts of thewideband LTE Release 10 carrier. The straightforward way to obtain thismay be by means of Carrier Aggregation (CA). CA implies that an LTERelease 10 terminal may receive multiple CC, where the CC may have, orat least the possibility to have, the same structure as a Release 8carrier. CA is illustrated in the schematic diagram of FIG. 4, where 5carriers of 20 MHz each are aggregated to form a bandwidth of 100 MHz. ACA-capable communication device, such as a UE, may be assigned a PrimaryCell (PCell) which is always activated, and one or more Secondary Cells(SCells), which may be activated or deactivated dynamically.

The number of aggregated CC as well as the bandwidth of the individualCC may be different for UL and DL. A symmetric configuration refers tothe case where the number of CCs in DL and UL is the same, whereas anasymmetric configuration refers to the case that the number of CCs isdifferent. It may be noted that the number of CCs configured in a cellmay be different from the number of CCs seen by a terminal: A terminalmay for example support more DL CCs than UL CCs, even though the cell isconfigured with the same number of UL and DL CCs.

In addition, a feature of CA may be the ability to perform cross-carrierscheduling. This mechanism may allow an (E)PDCCH on one CC to scheduledata transmissions on another CC by means of a 3-bit Carrier IndicatorField (CIF) inserted at the beginning of the (E)PDCCH messages. For datatransmissions on a given CC, a UE may expect to receive schedulingmessages on the (E)PDCCH on just one CC—either the same CC, or adifferent CC via cross-carrier scheduling; this mapping from (E)PDCCH toPDSCH may also be configured semi-statically.

LTE Measurements

A UE may perform periodic cell search and Reference Signal ReceivedPower (RSRP) and Reference Signal Received Quality (RSRQ) measurementsin Radio Resource Control (RRC) Connected mode. It may be responsiblefor detecting new neighbor cells, and for tracking and monitoringalready detected cells. The detected cells and the associatedmeasurement values may be reported to the network. Reports to thenetwork may be configured to be periodic or aperiodic based a particularevent.

Rel-12 LTE Discovery Reference Signal (DRS)

To share the channel in the unlicensed spectrum, the LAA SCell may notoccupy the channel indefinitely. One of the mechanisms for interferenceavoidance and coordination among small cells may be the SCell ON/OFFfeature, whereby when a small cell has no or low traffic, the small cellmay be turned off or dynamically blanked to reduce the interference toneighboring cells. In Rel-12 LTE, discovery signals were introduced toprovide enhanced support for SCell ON/OFF operations. A discovery signalmay be understood as a set of reference signals and synchronizationsequences that may be transmitted together in the same subframe in orderto facilitate synchronization, Radio Resource Management (RRM)measurements, and channel estimation. Specifically, these signals may beintroduced to handle a potentially severe interference situation,particularly on the synchronization signals, resulting from densedeployment, as well as to reduce UE inter-frequency measurementcomplexity.

A so called DRS occasion may be understood herein as the time periodwherein DRS are transmitted, e.g., from a cell. The discovery signals orDiscovery Reference Signal (DRS) in a DRS occasion may be comprised ofthe Primary Synchronization Signal (PSS), Secondary SynchronizationSignal (SSS), the CRS and when configured, the Channel State InformationReference Signals (CSI-RS). The PSS and SSS may be used for coarsesynchronization, when needed, and for cell identification. The CRS maybe used for fine time and frequency estimation and tracking and may alsobe used for cell validation, i.e., to confirm the cell IDentity (ID)detected from the PSS and SSS. The CSI-RS is another signal that may beused in dense deployments for cell or transmission point identification.FIG. 5 shows the presence of these signals in a DRS occasion of lengthequal to two subframes and also shows the transmission of the signalsover two different cells or Transmission Points (TP).

FIG. 5 is a schematic diagram of the OFDM subcarriers and symbols in twosubframes, wherein the dotted RE with light background represent SSS,the dotted RE with black background represent PSS, the striped RErepresent CRS, the black RE represent empty RE, and the checkered RErepresent CSI-RS. The two subframes are separated by a bold verticalbar.

The DRS occasion corresponding to transmissions from a particular cellmay range in duration from one to five subframes for Frequency DivisionDuplex (FDD), and two to five subframes for Time Division Duplex (TDD).The subframe in which the SSS occurs may mark the starting subframe ofthe DRS occasion. This subframe is either subframe 0 or subframe 5 inboth FDD and TDD. In TDD, the PSS may appear in subframe 1 and subframe6, while in FDD the PSS may appear in the same subframe as the SSS. TheCRS may be transmitted in all DL subframes and Downlink Pilot TimeSlot(DwPTS) regions of special subframes.

The discovery signals may be useable by the UE for performing cellidentification, RSRP and RSRQ measurements. The RSRP measurementdefinition based on discovery signals may be the same as in priorreleases of LTE.

In Rel-12, RSRP measurements based on the CRS and CSI-RS in the DRSoccasions and RSRQ measurements based on the CRS in the DRS occasionshave been defined. As stated earlier, discovery signals may be used in asmall cell deployment where the cells are being turned off and on or ina general deployment where the on/off feature is not being used. Forinstance, discovery signals may be used to make RSRP measurements ondifferent CSI-RS configurations in the DRS occasion being used within acell, which may enable the detection of different transmission points ina shared cell.

The provision of DRS timing information may be done via a DiscoveryMeasurement Timing Configuration (DMTC) that may be signaled to the UE.The DMTC may provide a window with a duration of 6 milliseconds (ms)occurring with a certain periodicity and timing within which the UE mayexpect to receive discovery signals. The duration of 6 ms may be thesame as the measurement gap duration as defined currently in LTE and mayallow the measurement procedures at the UE for discovery signals to beharmonized regardless of the need for measurement gaps. Only one DMTCmay be provided per carrier frequency including the current servingfrequencies. The UE may expect that the network will transmit discoverysignals so that all cells that are intended to be discoverable on acarrier frequency transmit discovery signals within the DMTCs.Furthermore, when measurement gaps may be needed, it may be expectedthat the network may ensure sufficient overlap between the configuredDMTCs and measurement gaps.

Wireless Local Area Network (WLAN)

In typical deployments of WLAN, Carrier Sense Multiple Access withCollision Avoidance (CSMA/CA) may be used for medium access. This meansthat the channel may be sensed to perform a Clear Channel Assessment(CCA), and a transmission may be initiated only if the channel isdeclared as Idle. In case the channel is declared as Busy, thetransmission may be essentially deferred until the channel is deemed tobe Idle. When the range of several Access Points (APs) using the samefrequency overlap, this may mean that all transmissions related to oneAP may be deferred in case a transmission on the same frequency to orfrom another AP, which is within range, may be detected. Effectively,this may mean that if several APs are within range, they may have toshare the channel in time, and the throughput for the individual APs maybe severely degraded. A general illustration on an example of the ListenBefore Talk (LBT) mechanism or process is shown in FIG. 6. The LBTprocedure may either be frame-based or load-based. The frame based LBTframework may allow an equipment to perform a CCA per fixed frame periodfor a duration of T1, as illustrated in FIG. 6 by a circled 1. CCA maybe performed using Energy detection. If the channel is found to beavailable after the CCA operation, as indicated by a check sign in theFigure, the equipment may transmit immediately up to the maximum allowedchannel occupancy time, for example 10 ms, where this time may bereferred to as the channel occupancy time, T2, and denoted by circled 2in FIG. 6. In the example of FIG. 6, a communication device may performan extended CCA under the load-based LBT framework, as described forexample in Europe regulation EN 301.893 v 1.7.1, load-based LBTprocedure. The extended CCA under the load-based LBT framework may alsobe referred to herein as a complete random backoff procedure, and isindicated in the Figure with a circled 3. Basically, a complete randombackoff procedure may be understood as involving drawing a random numberprior to transmission, and determining that the channel has been idlefor said number of observation slots, i.e., CCA, before commencingtransmission. The range from which the random number is drawn may bemodified, depending on whether previous transmissions were successful orunsuccessful. During the random backoff procedure, before the equipmenttransmits for the first time on an operating channel, the equipment maycheck if the channel is currently idle. At the end of the required idleperiod, the equipment may resume CCA for channel access. If the channelis not idle, the equipment draws a random number N of CCAs after whichthe channel has to be available before transmission may occur. N, inFIG. 6 is 3. A counter may be set to 3, as indicated in FIG. 6, and 1 issubtracted from the current N value, every time the channel is observedto be available after a CCA. If the channel is found to be busy afterthe CCA operation, as indicated by a cross sign, no value is subtracted,or a 0 value is subtracted. When N is counted down to 0, transmissionmay take place during the second period indicated by “Transmission” inFIG. 6, starting from the left end of the Figure. During the secondperiod indicated by the circled number 2 in FIG. 6, starting from theleft end of the Figure, data may be transmitted and control signals maybe sent without a CCA check during the period denoted as “Ctrl” by acircled 4.

In contrast to a complete random backoff procedure, a short CCA may beunderstood as observing the channel for a fixed, short number of CCAslots, such as one slot, without drawing a random number, as describedabove.

In LAA, described below, DRS that may be transmitted without PDSCH inthe same subframe/s may be sent after a short Clear Channel Assessment(CCA), based on a single sensing interval. In other words, a completerandom backoff procedure may not be required to be followed when sendingDRS without PDSCH.

Licensed-Assisted Access (LAA) to Unlicensed Spectrum Using LTE

Up to now, the spectrum used by LTE may be dedicated to LTE. This mayhave the advantage that the LTE system may not need to care about thecoexistence issue and the spectrum efficiency may be maximized. However,the spectrum allocated to LTE is limited, which may not meet the everincreasing demand for larger throughput from applications and/orservices. Therefore, a new study item has been initiated in 3GPP onextending LTE to exploit unlicensed spectrum in addition to licensedspectrum. Unlicensed spectrum may, by definition, be simultaneously usedby multiple different technologies. Therefore, LTE may need to considerthe coexistence issue with other systems such as IEEE 802.11 (Wi-Fi).Operating LTE in the same manner in unlicensed spectrum as in licensedspectrum may seriously degrade the performance of Wi-Fi, as Wi-Fi maynot transmit once it detects the channel is occupied.

Furthermore, one way to utilize the unlicensed spectrum reliably may beto transmit essential control signals and channels on a licensedcarrier. That is, as shown in FIG. 7, a UE may be connected to a PCellin the licensed band and one or more SCells in the unlicensed band.Herein, a SCell in unlicensed spectrum may be referred to as aLicense-Assisted Secondary Cell (LA SCell) or Licensed-Assisted AccessCell. FIG. 7 illustrates LAA to unlicensed spectrum using LTE carrieraggregation.

Further detailed information on some aspects discussed herein may befound in: 3GPP TS 36.211, V11.4.0 (2013-September), 3rd GenerationPartnership Project; Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channelsand Modulation, Release 11, in 3GPP TS 36.213, V11.4.0 (2013-September),3rd Generation Partnership Project; Technical Specification Group RadioAccess Network; Evolved Universal Terrestrial Radio Access (E-UTRA);Physical layer procedures, Release 11, and 3GPP TS 36.331, V11.5.0(2013-September), 3rd Generation Partnership Project; TechnicalSpecification Group Radio Access Network; Evolved Universal TerrestrialRadio Access (E-UTRA); Radio Resource Control (RRC), Release 11.

In existing LTE communication methods, a significant delay in accessingthe medium may be incurred when networks are congested with multiplenodes contending for channel access.

SUMMARY

It is an object of embodiments herein to improve transmission of controlinformation in wireless communications networks.

According to a first aspect of embodiments herein, the object isachieved by a method performed by a first communication device. Themethod is for sending one or more control signals to a secondcommunication device. The first communication device and the secondcommunication device operate in a wireless communications network. Thefirst communication device determines, during a first period, that atransmission medium is available for sending the one or more controlsignals to the second communication device. The first communicationdevice then sends, to the second communication device, the one or morecontrol signals along with a discovery signal, via the transmissionmedium. The discovery signal and the one or more control signals aresent without data after the first period. The first period is shorterthan a second period for determining that the transmission medium isavailable for sending the data.

According to a second aspect of embodiments herein, the object isachieved by the first communication device configured to send one ormore control signals to the second communication device. The firstcommunication device and the second communication device are configuredto operate in the wireless communications network. The firstcommunication device is configured to determine, during the firstperiod, that the transmission medium is available for sending the one ormore control signals to the second communication device. The firstcommunication device is further configured to send, to the secondcommunication device, the one or more control signals along with thediscovery signal, via the transmission medium. The discovery signal andthe one or more control signals are configured to be sent without dataafter the first period. The first period is shorter than the secondperiod configured for determining that the transmission medium isavailable for sending the data.

According to a third aspect of embodiments herein, the object isachieved by a computer program. The computer program comprisesinstructions which, when executed on at least one processor, cause theat least one processor to carry out the method according to embodimentsherein.

According to a fourth aspect of embodiments herein, the object isachieved by computer-readable storage medium. The computer-readablestorage medium has stored thereon a computer program comprisinginstructions which, when executed on at least one processor, cause theat least one processor to carry out the method according to embodimentsherein.

By the first communication device determining that the transmissionmedium is available during the first period, and then sending the one ormore control signals along with the discovery signal to the secondcommunication device, after the first period, the first communicationdevice may send the one or more control signals faster, that is, withless delay, than with existing methods. This is because the first periodis shorter than the second period for determining that the transmissionmedium is available for sending the data, since control signals areaccording to existing methods sent along with data, e.g., in unlicensedspectrum. In a particular example, the first communication device maysend the one or more control signals, without the need to complete arandom backoff procedure. Therefore, fast control signaling may beachieved and UL channel starvation may be mitigated in congested networkscenarios since a separate period for determining that the transmissionmedium is available is not needed for the first communication device tosend UL e.g., transmission grants, improving the overall function of thewireless communications network.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments herein are described in more detail withreference to the accompanying drawings, the content of which is brieflysummarized in the following list.

FIG. 1 is a schematic diagram illustrating the basic LTE DL physicalresource.

FIG. 2 is a schematic diagram illustrating the LTE time-domainstructure.

FIG. 3 is a schematic diagram illustrating a normal DL subframe in LTE.

FIG. 4 is a schematic illustrating CA.

FIG. 5 is a schematic diagram of two subframes comprising DRS.

FIG. 6 is a schematic diagram illustrating an example of the LBTmechanism.

FIG. 7 is a schematic diagram illustrating LAA to unlicensed spectrumusing LTE carrier aggregation.

FIG. 8 is a schematic diagram illustrating embodiments of a wirelesscommunications network, according to embodiments herein.

FIG. 9 is a flowchart depicting embodiments of a method in a firstcommunication device, according to embodiments herein.

FIG. 10 is a schematic diagram illustrating an example of embodiments ofa method in a first communication device, according to embodimentsherein.

FIG. 11 is a schematic block diagram illustrating embodiments of a firstcommunication device, according to embodiments herein.

DETAILED DESCRIPTION Terminologies

The following commonly terminologies are used in the embodiments and areelaborated below:

Radio network node: In some embodiments the non-limiting term radionetwork node is more commonly used and it refers to any type of networknode serving UE and/or connected to other network node or networkelement or any radio node from where a UE may receive a signal. Examplesof radio network nodes are Node B, Base Station (BS), Multi-StandardRadio (MSR) radio node such as MSR BS, eNode B, network controller,Radio Network Controller (RNC), base station controller, relay, donornode controlling relay, Base Transceiver Station (BTS), Access Point(AP), transmission points, transmission nodes, Remote Radio Unit (RRU),Remote Radio Head (RRH), nodes in Distributed Antenna System (DAS) etc.

Network node: In some embodiments a more general term “network node” isused and it may correspond to any type of radio network node or anynetwork node, which communicates with at least a radio network node.Examples of network node are any radio network node stated above, corenetwork node, e.g., Mobile Switching Centre (MSC), Mobility ManagementEntity (MME) etc. . . . , Operation and Maintenance (O&M), OperatingSupport Systems (OSS), Self-Organizing Network (SON), positioning node,e.g., Evolved Serving Mobile Location Center (E-SMLC), Minimization ofDrive Test (MDT) etc.

User equipment: In some embodiments the non-limiting term user equipment(UE) is used and it refers to any type of wireless device communicatingwith a radio network node in a cellular or mobile communication system.Examples of UE are target device, device to device UE, machine type UEor UE capable of machine to machine communication, Personal DigitalAssistant (PDA), iPAD, Tablet, mobile terminals, smart phone, LaptopEmbedded Equipped (LEE), Laptop Mounted Equipment (LME), USB donglesetc.

The embodiments herein also apply to the multi-point carrier aggregationsystems.

As part of the development of embodiments herein, a problem with exitingmethods will first be identified and discussed.

Currently, control information such as resource allocation grants, sentvia PDCCH/EPDCCH on unlicensed carriers may be transmitted only after acomplete random backoff procedure is performed and, when data, e.g., thePDSCH, is also present. A significant delay in accessing the medium maytherefore be incurred when networks are congested with multiple nodescontending for channel access.

In order to expedite the transmission of control signals, embodimentsherein may relate to transmission of control signals along withdiscovery reference signals. Particular examples herein may teach how toexploit the short CCA for quick DRS channel access without PDSCH bysending control information such as resource allocation grants alongwith the DRS. The grants may be for UL transmission, DL transmissions infuture subframes, cross-carrier grants or joint grants across multiplecarriers, and common search space control signaling.

Embodiments will now be described more fully hereinafter with referenceto the accompanying drawings, in which examples are shown. In thissection, the embodiments herein will be illustrated in more detail by anumber of exemplary embodiments. It should be noted that the exemplaryembodiments herein are not mutually exclusive. Components from oneembodiment may be tacitly assumed to be present in another embodimentand it will be obvious to a person skilled in the art how thosecomponents may be used in the other exemplary embodiments.

Note that although terminology from 3GPP LTE has been used in thisdisclosure to exemplify the embodiments herein, this should not be seenas limiting the scope of the embodiments herein to only theaforementioned system. Other wireless systems with similar requirementsto those of LTE for LAA or standalone LTE-U, may also benefit fromexploiting the ideas covered within this disclosure.

FIG. 8 depicts an example of a wireless communications network 100,sometimes also referred to as a cellular radio system, cellular networkor wireless communications system, in which embodiments herein may beimplemented. The wireless communications network 100 may for example bea network such as a Long-Term Evolution (LTE), e.g. LTE FrequencyDivision Duplex (FDD), LTE Time Division Duplex (TDD), LTE Half-DuplexFrequency Division Duplex (HD-FDD), LTE operating in an unlicensed band,Wideband Code Division Multiple Access (WCDMA), 5G system or anycellular network or system with similar requirements to those of LTE forLAA or standalone LTE in Unlicensed (LTE-U). Thus, although terminologyfrom 3GPP LTE may be used in this disclosure to exemplify embodimentsherein, this should not be seen as limiting the scope of the embodimentsherein to only the aforementioned system.

The wireless communications network 100 comprises a plurality ofcommunication devices, such as the first communication device 101, andthe second communication device 102. Any of the first communicationdevice 101 and the second communication device 102 may be a network nodesuch as network node 110 described below, or a wireless device such aswireless device 120 described below. The first communication device 101is different than the second communication device 102. Typically, on theDL, the first communication device 101 will be the network node 110 andthe second communication device 102 will be the wireless device 120.This corresponds to the non-limiting particular example illustrated inFIG. 8. Also typically, on the UL, the first communication device 101will be the wireless device 120 and the second communication device 102will be the network node 110. In Device to Device (D2D) communications,both of the first communication device 101 and the second communicationdevice 102 may be different wireless devices, both in the UL and in theDL.

The wireless communications network 100 comprises a plurality of networknodes whereof the network node 110 is depicted in FIG. 8. The networknode 110 may be a transmission point such as a radio base station, forexample an eNB, an eNodeB, or an Home Node B, an Home eNode B or anyother network node capable to serve a wireless device, such as a userequipment or a machine type communication device in the wirelesscommunications network 100.

The wireless communications network 100 covers a geographical areawhich, which in some embodiments may be divided into cell areas, whereineach cell area is served by a network node, although, one network nodemay serve one or several cells. In the non-limiting example depicted inFIG. 8, the network node 110 serves a first cell 131, which may be aprimary cell. The primary cell 131 is typically in licensed spectrum. InFIG. 8, the network node 110 also serves a second cell 132, which may bea licensed-assisted access cell, also referred to herein aslicensed-assisted access secondary cell 132, as defined above. Thelicensed-assisted access cell 132 is in unlicensed spectrum. Since theprimary cell 131 and the licensed-assisted access cell 132 are used forcommunication between the first communication device 101 and the secondcommunication device 102, the primary cell 131 and the licensed-assistedaccess cell 132 may be understood as being associated with the firstcommunication device 101 and the second communication device 102. Thenetwork node 100 may be of different classes, such as, e.g., macroeNodeB, home eNodeB or pico base station, based on transmission powerand thereby also cell size. Typically, the wireless communicationsnetwork 100 may comprise more cells similar to the first cell 131 andthe second cell 132, served by their respective network node. This isnot depicted in FIG. 8 for the sake of simplicity. In other examplesthan those depicted in FIG. 8, wherein the wireless communicationsnetwork 100 is a non-cellular system, any of the network node 110 mayserve receiving nodes with serving beams. The network node 110 maysupport one or several communication technologies, and its name maydepend on the technology and terminology used. In 3GPP LTE, the networknode 110, which may be referred to as eNodeB or even eNB, may bedirectly connected to one or more core networks.

A wireless device 120 also referred to herein as a user equipment or UEis located in the wireless communication network 100. The wirelessdevice 120 may e.g. a wireless communication device such as a UE whichis also known as e.g. mobile terminal, wireless terminal and/or mobilestation, a mobile telephone, cellular telephone, or laptop with wirelesscapability, just to mention some further examples. The wireless device120 may be, for example, portable, pocket-storable, hand-held,computer-comprised, or a vehicle-mounted mobile device, enabled tocommunicate voice and/or data, via the RAN, with another entity, such asa server, a laptop, a PDA, or a tablet computer, sometimes referred toas a tablet with wireless capability, Machine-to-Machine (M2M) device,device equipped with a wireless interface, such as a printer or a filestorage device, modem, or any other radio network unit capable ofcommunicating over a wired or radio link in a communications system. Thewireless device 120 is enabled to communicate wirelessly in the wirelesscommunications network 100. The communication may be performed e.g., viaa RAN and possibly one or more core networks, comprised within thewireless communications network 100.

The first communication device 101 is configured to communicate withinthe wireless communications network 100 with the second communicationdevice 102 over a first radio link 141 in the first cell 131, and over asecond radio link 142 in the second cell 132.

Several embodiments are comprised herein. More specifically, thefollowing are embodiments related to the first communication device 101.

Embodiments of a method performed by the first communication device 101for sending one or more control signals to the second communicationdevice 102, will now be described with reference to the flowchartdepicted depicted in FIG. 9. The first communication device 101 and thesecond communication device 102 operate in the wireless communicationsnetwork 100.

Components from one embodiment may be tacitly assumed to be present inanother embodiment and it will be obvious to a person skilled in the arthow those components may be used in the other exemplary embodiments.

Action 901

During the course of communications between the first communicationdevice 101 and the second communication device 102, the firstcommunication device 101 may need to send one or more control signals tothe second communication device 102. A control signal may be understoodas a set of e.g., coded bits that carry scheduling information fordownlink or uplink data transmissions. The one or more control signalsmay comprise, for example, one or more of: an uplink grant, a downlinkgrant, a cross carrier grant, a joint grant, and common search spacecontrol signalling. The sending of the one or more control signals mayoccur via a transmission medium, which may be a carrier on unlicensedspectrum.

In order to send the one or more control signals to the secondcommunication device 102, in this Action, the first communication device101 first determines, during a first period, that the transmissionmedium is available for sending the one or more control signals to thesecond communication device 102. Sending may be understood astransmitting. The determining that the transmission medium is availablein this Action may be understood, for example, as determining that thetransmission medium is idle. That is, that other communication devicesare not transmitting in the transmission medium during the first period.In some particular examples, the determining Action 901 may compriseperforming a short CCA procedure, e.g., a single sensing interval, asconfigured, and determining that the transmission medium, e.g., atransmission channel, is idle. In other embodiments, the determining inthis Action 901 may be performed without having to sense for 1 CCA slot.

The first period may be understood as a time period that has a firstduration. The first period may be, for example, a short CCA. As anon-limiting example, the short CCA may be of the duration of a CCAsensing slot used in the random backoff procedure, e.g., 9 μs. Asanother example, the short CCA may be of the duration of a defer periodused in the random backoff procedure, e.g., the Arbitration Inter-FrameSpace (AIFS), Distributed Coordination Function Inter-Frame Space(DIFS), or Point Coordination Function Inter-Frame Space (PIFS), asdescribed in e.g., IEEE Std 802.11™—2012.

In some embodiments, the carrier may be a secondary carrier. Forexample, the carrier may be a secondary carrier configured as a servingcell on unlicensed spectrum, such as the second cell 132. The carriermay be aggregated with a primary carrier configured as another servingcell on a licensed or unlicensed channel, such as the first cell 131.

Action 902

Once the first communication device 101 has determined that thetransmission medium is available, in this Action, the firstcommunication device 101 sends, e.g., transmits, to the secondcommunication device 102, the one or more control signals along with adiscovery signal, via the transmission medium, e.g., via the secondradio link 142. The discovery signal and the one or more control signalsare sent without data after the first period. The first period isshorter than a second period for determining that the transmissionmedium is available for sending the data.

The second period may be understood as another time period that has asecond duration. The duration of the first time period may be a fractionof the duration of the second time period. In some examples, the firstperiod may be a time period to perform a short CCA and the second periodmay be, for example, a complete random backoff procedure, e.g., such asin LTE. The complete random backoff procedure may have a variableduration from procedure to procedure, but overall, according toembodiments herein the one or more control signals may be sent aftere.g. a few microseconds, as opposed to after e.g., tens or hundreds ofmicroseconds.

The data may be, for example, a data channel such as the PDSCH. The oneor more control signals sent may be sent in downlink in one of: a PDCCH,and an EPDCCH. The discovery signal may be, for example, a DRS in LTE.

In some embodiments, the sending the one or more control signals alongwith the discovery signal may comprise sending the one or more signalswithin a DRS occasion comprising the discovery signal.

The sending the one or more control signals along with the discoverysignal may be understood as sending the one or more control signals in asame set of time-frequency resources as the discovery signal, which maybe referred to herein as a first set of time-frequency resources. Anexample of the first set of time-frequency resources may be one or moresubframes, e.g., in LTE, which may be referred to herein as a first oneor more subframes. That is, in some examples, the sending the one ormore control signals along with the discovery signal may comprisesending the one or more signals in the same subframe wherein thediscovery signal is sent. The DRS transmission burst within a DRSoccasion may span a variable number of subframes, including partialsubframes. In particular, the sending the one or more control signalsalong with the discovery signal may comprise sending the one or moresignals within one or more subframes within a DRS occasion comprisingthe discovery signal. Therefore, the sending the one or more controlsignals along with the discovery signal may comprise sending the one ormore signals in the same one or more subframes wherein the discoverysignal is sent. For example, the (E)PDCCHs for one or more UEs may besent in the same subframe/s that contain the DRS. In further particularexamples, the (E)PDCCH may be transmitted in the PDSCH region, e.g.,from OFDM symbol #3 onwards as an example. The PDCCH may be sent in thefirst 3 OFDM symbols, e.g., in the “control region” in FIG. 3.

The DRS with resource grants may be sent periodically or aperiodically.

In some embodiments, the data may be sent by the first communicationdevice 101 to the second communication device 102 after the secondperiod in a second set of time-frequency resources, e.g., a second oneor more subframes in LTE.

The following is a description of different groups of examples ofembodiments herein, which are illustrated taking DRS as an example ofthe discovery signal.

DRS with UL Grants

In a first group of examples, UL resource grants may be sent by thefirst communication device 101 in the subframe/s containing DRS within aDRS occasion. These grants may be used to indicate PUSCH allocations onan upcoming Transmission-Time Interval (TTI), for example 2 ms or 4 msafter the DRS subframe. Grants for multiple upcoming TTIs may be sent inthe same subframe.

In another exemplary implementation, the UL grant/s sent with the DRSmay be multi-subframe grants that may be valid for a specific range ofmultiple UL subframes, or that may be valid for a specific time windowon the UL.

DRS with DL Grants

In a second group of examples, the resource grants sent by the firstcommunication device 101 with the DRS may correspond to DL PDSCH grantsfor future subframes or upcoming burst of subframes.

DRS with Cross-Carrier or Joint Grants

In a third group of examples, cross-carrier scheduling grants for DL orUL transmission on another carrier may be sent by the firstcommunication device 101 along with the DRS on the scheduling SCell,such as the second cell 132. In a multi-carrier scenario, the firstcommunication device 101, e.g., an eNB, may transmit DRS with controlsignals and no PDSCH on one or more unlicensed carriers while sendingPDSCH with full random backoff on other unlicensed carriers.

In another exemplary implementation, the scheduling grant that may besent by the first communication device 101 with DRS on the schedulingcell may be a joint grant which is valid across multiple carriers in thesame TTI, or burst of TTI's.

The first, second and third group of examples may be combined. For themulti-subframe UL scheduling and the DL scheduling for future frames,the DCI may need a new field which specifies the number of subframes forwhich the resource allocation indicated by the DCI may be valid.

DRS with Common Search Space Control Signaling

In a fourth group of examples, control signals associated with the(E)PDCCH common search space of UEs, that is, the region of the DLsubframe wherein all UEs may check for control signals, such as systeminformation or transmit power control commands for example, may be sentby the first communication device 101 in DRS subframe/s without PDSCH inthe DRS occasion with the DRS being transmitted either with no CCA orwith a short CCA.

A principle of embodiments herein, may be understood as relating tosending one or more control signals, such as resource allocation grantsand other control signals, in DRS without PDSCH so as to use a short CCAprior to channel access. This is illustrated in the example of FIG. 10.FIG. 10 is a schematic diagram, wherein the black blocks represent datatransmissions comprising PDSCH outside of the DRS occasions. The DRSoccasions comprising the discovery signals and the one or more controlsignals are represented by the white blocks comprising the letter “D”.FIG. 10 illustrates fast control signaling sent along with DRS withoutPDSCH, where (E)PDCCH is sent in the DRS subframe/s by the firstcommunication device 101, an eNB in the non-limiting example of FIG. 10.The allocation grants or control signals may also be sent by the firstcommunication device 101 using PDCCH.

Embodiments herein may be understood as teaching how to exploit theshort CCA for quick DRS channel access without PDSCH by the firstcommunication device 101 sending resource allocation grants along withthe DRS. The grants may be for UL transmission, DL transmissions infuture subframes, cross-carrier grants or joint grants across multiplecarrier, and common search space control signaling.

Accordingly, an advantage of embodiments herein is therefore that fastcontrol signaling may be achieved for LAA and/or standalone LTE-U.

Another advantage of embodiments herein is that UL channel starvationmay be mitigated in congested network scenarios.

To perform the method actions described above in relation to FIGS. 9and/or 10, the first communication device 101 is configured to send theone or more control signals to the second communication device 102. Thefirst communication device 101 may comprise the following arrangementdepicted in FIG. 11. As already mentioned, the first communicationdevice 101 and the second communication device 102 are furtherconfigured to operate in the wireless communications network 100.

The detailed description of some of the following corresponds to thesame references provided above, in relation to the actions described forthe first communication device 101, and will thus not be repeated here.For example, the one or more control signals may comprise one or moreof: an uplink grant, a downlink grant, a cross carrier grant, a jointgrant, and common search space control signalling.

The first communication device 101 is configured to, e.g., by means of adetermining module 1101 configured to, determine, during the firstperiod, that the transmission medium is available for sending the one ormore control signals to the second communication device 102.

The determining module 1101 may be a processor 1104 of the firstcommunication device 101, or an application running on such processor.

In some embodiments, the transmission medium may be a carrier onunlicensed spectrum. The carrier may be a secondary carrier.

The first communication device 101 is further configured to, e.g., bymeans of a sending module 1102 configured to, send, to the secondcommunication device 102, the one or more control signals along with thediscovery signal, via the transmission medium, the discovery signal andthe one or more control signals being configured to be sent without dataafter the first period, the first period being shorter than a secondperiod configured for determining that the transmission medium isavailable for sending the data.

The sending module 1102 may be the processor 1104 of the firstcommunication device 101, or an application running on such processor.

The first period may be a short CCA, and the second period may be acomplete random backoff procedure.

The one or more control signals sent may be sent in downlink in one of:a PDCCH, and an EPDCCH.

The discovery signal may be a DRS in LTE.

The data may be a PDSCH.

In some embodiments, to send the one or more control signals along withthe discovery signal may comprise to send the one or more signals withina DRS occasion comprising the discovery signal.

To send the one or more control signals along with the discovery signalmay comprise to send the one or more signals in the same subframewherein the discovery signal is configured to be sent.

The first communication device 101 may comprise other modules 1103.

The first communication device 101 may comprise an interface unit tofacilitate communications between the first communication device 101 andother nodes or devices, e.g., the second communication device 102. Theinterface may, for example, include a transceiver configured to transmitand receive radio signals over an air interface in accordance with asuitable standard.

The embodiments herein may be implemented through one or moreprocessors, such as the processor 1104 in the first communication device101 depicted in FIG. 11, together with computer program code forperforming the functions and actions of the embodiments herein. Theprogram code mentioned above may also be provided as a computer programproduct, for instance in the form of a data carrier carrying computerprogram code for performing the embodiments herein when being loadedinto the in the first communication device 101. One such carrier may bein the form of a CD ROM disc. It is however feasible with other datacarriers such as a memory stick. The computer program code mayfurthermore be provided as pure program code on a server and downloadedto the first communication device 101. The computer program code mayalso be provided as a service from the cloud.

The first communication device 101 may further comprise a memory 1105comprising one or more memory units. The memory 1105 is arranged to beused to store obtained information, store data, configurations,schedulings, and applications etc. to perform the methods herein whenbeing executed in the first communication device 101.

In some embodiments, the first communication device 101 may receiveinformation from the second communication device 102, through areceiving port 1106. In some embodiments, the receiving port 1106 maybe, for example, connected to one or more antennas in firstcommunication device 101. In other embodiments, the first communicationdevice 101 may receive information from another structure in thewireless communications network 100 through the receiving port 1106.Since the receiving port 1106 may be in communication with the processor1104, the receiving port 1106 may then send the received information tothe processor 1104. The receiving port 1106 may also be configured toreceive other information.

The processor 1104 in the first communication device 101 may be furtherconfigured to transmit or send information to e.g., the secondcommunication device 102, through a sending port 1107, which may be incommunication with the processor 1104, and the memory 1105.

The first communication device 101 may comprise an interface unit tofacilitate communications between the first communication device 101 andother nodes or devices, e.g., the second communication device 102. Theinterface may, for example, include a transceiver configured to transmitand receive radio signals over an air interface in accordance with asuitable standard.

Those skilled in the art will also appreciate that the determiningmodule 1101, the sending module 1102 and the other modules 1103described above may refer to a combination of analog and digitalmodules, and/or one or more processors configured with software and/orfirmware, e.g., stored in the memory 1105, that, when executed by theone or more processors such as the processor 1104, perform the methodsas described above. One or more of these processors, as well as theother digital hardware, may be included in a single Application-SpecificIntegrated Circuit (ASIC), or several processors and various digitalhardware may be distributed among several separate components, whetherindividually packaged or assembled into a System-on-a-Chip (SoC).

Also, in some embodiments, the different modules 1101-1103 describedabove may be implemented as one or more applications running on one ormore processors such as the processor 1104.

Thus, the methods according to the embodiments described herein for thefirst communication device 101 may be respectively implemented by meansof a computer program 1108 product, comprising instructions, i.e.,software code portions, which, when executed on at least one processor1104, cause the at least one processor 1104 to carry out the actionsdescribed herein, as performed by the first communication device 101.The computer program 1108 product may be stored on a computer-readablestorage medium 1109. The computer-readable storage medium 1109, havingstored thereon the computer program 1108, may comprise instructionswhich, when executed on at least one processor 1104, cause the at leastone processor 1104 to carry out the actions described herein, asperformed by the first communication device 101. In some embodiments,the computer-readable storage medium 1109 may be a non-transitorycomputer-readable storage medium 1109, such as a CD ROM disc, or amemory stick. In other embodiments, the computer program 1108 productmay be stored on a carrier containing the computer program justdescribed, wherein the carrier is one of an electronic signal, opticalsignal, radio signal, or the computer-readable storage medium, asdescribed above.

When using the word “comprise” or “comprising” it shall be interpretedas non-limiting, i.e. meaning “consist at least of”.

The embodiments herein are not limited to the above described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention.

Also note that terminology such as eNodeB and UE should be consideringnon-limiting and does in particular not imply a certain hierarchicalrelation between the two; in general “eNodeB” could be considered asdevice 1 and “UE” device 2, and these two devices communicate with eachother over some radio channel. Herein, we also focus on wirelesstransmissions in the downlink, but the embodiments herein are equallyapplicable in the uplink for equivalent functions. For example, for theuplink, the first communication device 101 may send a newly-designedPUCCH together with a DeModulation Reference Signal (DMRS) or a SoundingReference Signal (SRS), where the PUCCH may carry some information aboutits upcoming contention-based PUSCH transmissions. In such UL scenarios,it may be noted that the UL RS may be referred to with a different namethan as a discovery signal.

The invention claimed is:
 1. A method performed by a first communicationdevice for sending one or more control signals to a second communicationdevice, the first communication device and the second communicationdevice operating in a wireless communications network, the methodcomprising: determining, during a first period, that a transmissionmedium is available for sending the one or more control signals to thesecond communication device; and sending, to the second communicationdevice, the one or more control signals along with a discovery signal,via the transmission medium, wherein the discovery signal and the one ormore control signals are sent without data after the first period, thefirst period being shorter than a second period for determining that thetransmission medium is available for sending the data.
 2. The methodaccording to claim 1, wherein the one or more control signals compriseone or more of: an uplink grant, a downlink grant, a cross carriergrant, a joint grant, and common search space control signalling.
 3. Themethod according to claim 1, wherein the transmission medium is acarrier on unlicensed spectrum.
 4. The method according to claim 3,wherein the carrier is a secondary carrier.
 5. The method according toclaim 1, wherein the first period is a short Clear Channel Assessment(CCA), and the second period is a complete random backoff procedure. 6.The method according to claim 1, wherein the one or more control signalsare sent in one of: a Physical Downlink Control Channel (PDCCH) and anEnhanced PDCCH (EPDCCH).
 7. The method according to claim 1, wherein thediscovery signal is a Discovery Reference Signal (DRS) in Long TermEvolution (LTE).
 8. The method according to claim 7, wherein the sendingof the one or more control signals along with the discovery signalcomprises sending the one or more signals within a DRS occasioncomprising the discovery signal.
 9. The method according to claim 8,wherein the sending of the one or more control signals along with thediscovery signal comprises sending the one or more signals in the samesubframe in which the discovery signal is sent.
 10. The method accordingto claim 1, wherein the data is a Physical Downlink Shared Channel(PDSCH).
 11. A non-transitory computer-readable storage medium, havingstored thereon a computer program, comprising instructions that, whenexecuted on at least one processor of a first communication device,cause the first communication device to: determine, during a firstperiod, that a transmission medium is available for sending one or morecontrol signals to a second communication device; and send, to thesecond communication device, the one or more control signals along witha discovery signal, via the transmission medium, wherein the discoverysignal and the one or more control signals are sent without data afterthe first period, the first period being shorter than a second periodfor determining that the transmission medium is available for sendingthe data.
 12. A first communication device configured to send one ormore control signals to a second communication device, the firstcommunication device and the second communication device being furtherconfigured to operate in a wireless communications network, the firstcommunication device comprising: an interface circuit configured forcommunicating with the second communication device; and processingcircuitry operatively associated with the interface circuit andconfigured to: determine, during a first period, that a transmissionmedium is available for sending the one or more control signals to thesecond communication device; and send, to the second communicationdevice, the one or more control signals along with a discovery signal,via the transmission medium, wherein the discovery signal and the one ormore control signals are sent without data after the first period, thefirst period being shorter than a second period configured fordetermining that the transmission medium is available for sending thedata.
 13. The first communication device according to claim 12, whereinthe one or more control signals comprise one or more of: an uplinkgrant, a downlink grant, a cross carrier grant, a joint grant, andcommon search space control signalling.
 14. The first communicationdevice according to claim 12, wherein the transmission medium is acarrier on unlicensed spectrum.
 15. The first communication deviceaccording to claim 14, wherein the carrier is a secondary carrier. 16.The first communication device according to claim 12, wherein the firstperiod is a short Clear Channel Assessment (CCA), and the second periodis a complete random backoff procedure.
 17. The first communicationdevice according to claim 12, wherein the one or more control signalssent are sent in one of: a Physical Downlink Control Channel (PDCCH) andan Enhanced PDCCH (EPDCCH).
 18. The first communication device accordingto claim 12, wherein the discovery signal is a Discovery ReferenceSignal (DRS) in Long Term Evolution (LTE).
 19. The first communicationdevice according to claim 18, wherein the processing circuitry isconfigured to send the one or more control signals along with thediscovery signal by sending the one or more signals within a DRSoccasion comprising the discovery signal.
 20. The first communicationdevice according to claim 19, wherein the processing circuitry isconfigured to send the one or more control signals along with thediscovery signal by sending the one or more signals in the same subframein which the discovery signal is sent.
 21. The first communicationdevice according to claim 12, wherein the data is a Physical DownlinkShared Channel (PDSCH).